M56 is a faint distant globular cluster in Lyra that's positioned close to the Cygnus border. At magnitude +8.3, it's one of the dimmer Messier globulars and a challenging binocular object, but easily visible in medium size amateur scopes. Instruments of the order of 250mm (10-inch) aperture or greater will resolve some of the member stars.
M56 was discovered by Charles Messier discovered on January 23, 1779. He described it as a "nebula without stars" and like many globulars was first resolved into stars by William Herschel. Another unusual feature of this object is it follows a retrograde orbit through the Milky Way. It has been suggested that M56 may have been acquired during the merger of a dwarf galaxy, of which Omega Centauri is the surviving nucleus.
M56 is located almost halfway along an imaginary line connecting beautiful double star Albireo (β Cyg - mag. +3.1) with Sulafat (γ Lyr - mag. +3.3). Since it's located in a dense part of the Milky Way, it's easy to miss, especially with small scopes. Positioned not far from M56 is the only other Messier object in Lyra, the Ring Nebula (M57).
Through 7x50 or 10x50 binoculars, M56 appears at best as a faint slightly fuzzy star. When viewed with larger 70mm or 80mm models, it looks obviously non-stellar. A 100mm (4-inch) telescope shows the cluster as a faint, round, diffuse ball of light with very little or no details discernible. A noticeable 5th magnitude star lies less than a degree to the northwest of the cluster. It's possible to resolve some of the outer stars using 250mm (10-inch) scopes with the brightest members being of 13th magnitude. The cluster displays a gradual, soft brightening from the outer regions towards the core. In total, it measures 8.8 arc minutes although visually it appears about half this size. Despite being overshadowed by M13 in Hercules, M56 is a fine globular in its own right.
M56 is 32,000 light-years distant, which corresponds to a spatial diameter of 84 light-years. It contains only a dozen or so variable stars and is estimated to be 13.7 billion years old. The globular is best seen from the Northern Hemisphere during the months of June, July and August.
M56 Data Table
|Object Type||Globular cluster|
|RA (J2000)||19h 16m 35s|
|DEC (J2000)||+30d 11m 05s|
|Apparent Size (arc mins)||8.8 x 8.8|
|Age (years)||13.7 Billion|
|Number of Stars||80,000|
|Notable Feature||Moving in a retrograde orbit through the Milky Way|